Question

Consider the following balanced reaction:
$2Ca\left(s\right)+O_2\left(g\right)\to 2CaO$
If 60 g of Ca is placed in a reaction chamber with 32 g of $O_2,$ which will be the limiting reactant and mass of the excess reactant left?

• A. Calcium; 8 g
• B. Oxygen; 16 g
• C. Calcium; 10 g
• D. Oxygen; 8 g

Answer 1

The correct option is A Calcium; 8 g

As per the reaction,
2 moles of Ca react with 1 mole of oxygen
$(2\times 40)$ g of Ca reacts with 32 g of oxygen
60 g will react with $\frac{32}{2\times 40}\times 60=24$ g of oxygen
Hence, Ca is the limiting reagent.
The amount of excess oxygen is = 32 g - 24 g = 8 g